Lithium manganese phosphate/carbon nanocomposites as cathode active materials for secondary lithium batteries

ABSTRACT

The invention relates to a lithium manganese phosphate/carbon nanocomposite as cathode material for rechargeable electrochemical cells with the general formula Li x Mn y M 1-y (PO 4 ) z /C where M is at least one other metal such as Fe, Ni, Co, Cr, V, Mg, Ca, Al, B, Zn, Cu, Nb, Ti, Zr, La, Ce, Y, x=0.8-1.1, y=0.5-1.0, 0.9&lt;z&lt;1.1, with a carbon content of 0.5 to 20% by weight, characterized by the fact that it is obtained by milling of suitable precursors of Li x Mn y M 1-y (PO 4 ) Z  with electro-conductive carbon black having a specific surface area of at least 80 m 2 /g or with graphite having a specific surface area of at least 9.5 m 2 /g or with activated carbon having a specific surface area of at least 200 m 2 /g. The invention also concerns a process for manufacturing said nanocomposite.

FIELD OF THE INVENTION

The invention relates to a lithium manganese metal phosphate/carbonnanocomposite as cathode material for rechargeable electrochemicalcells.

STATE OF THE ART

Rechargeable batteries of high energy density and long lifetime based onthe reversible intercalation of lithium into certain materials haveenabled the wide distribution of light and compact electronic devices,such as mobile phones and portable computers. However, the use ofcertain cathode materials, such as LiCoO₂, has given rise to concernsbecause of the toxicity of cobalt and the danger of fire and explosiondue to oxygen liberation and violent reaction with the organicelectrolyte on overcharging or at elevated temperature (thermalrunaway). Moreover cobalt is a rather rare and hence expensive element.Other materials, such as LiMn₂O₄ suffer from poor long term stability.

Lithium metal phosphates with olivine structure have emerged as apromising alternative as cathode materials, since the oxygen is stronglycovalently bound in PO₄ ³⁻, preventing the release of oxygen even underextreme conditions. In addition the inductive effect of PO₄ ³⁻ raisesthe redox potential of the metal centre, rendering the use of abundantand cheap metals such as iron and manganese possible. Thus, LiFePO₄yields a voltage of 3.4 V against lithium and remains stable overthousands of charge/discharge cycles, even upon overcharge and atelevated temperature. LiMnPO₄ gives an even higher voltage of 4.1 Vagainst lithium, which is near the stability limit of common non-aqueouselectrolytes and more compatible with classic systems, such as LiCoO₂,LiAl_(0.05)Co_(0.15)Ni_(0.8)O₂ or LiMn₂O₄. Thanks to the higher voltageLiMnPO₄ offers a superior energy density to LiFePO₄, which is importantfor many applications, especially battery electric vehicles.¹ However,only solid solutions LiMn_(y)Fe_(1-y)PO₄ were reported to beelectrochemically active.²⁻⁴ Still, the capacity ofLiMn_(0.5)Fe_(0.5)PO₄ was limited to 80 mAh/g, which is less than halfthe theoretical capacity of 170 mAh/g.

Almost full capacity has been reported for LiMnPO₄ andLi_(1-x)Mn_(y)Fe_(1-y)PO₄ prepared by ball milling of the precursors(MnCO₃, FeC₂O₄.2H₂O, NH₄H₂PO₄ and Li₂CO₃) with acetylene black andsubsequent firing under inert gas atmosphere.⁵⁻¹⁶ It was claimed thatthis results in a grain size of Li_(1-x)Mn_(y)Fe_(1-y)PO₄ not largerthan 10 μm, with the BET specific surface area not being less than 0.5m²/g.^(5,6,8-10,15) At a carbon content of 10% and a current density of0.28 mA/cm² a capacity of 164 mAh/g was reported for a Mn content ofy=0.75.¹⁶ Unfortunately, neither the charge/discharge rate nor theloading of active electrode material were indicated by the authors, butassuming a typical loading of 34 mg/cm² cited in their patentapplication¹⁵ a current density of 0.28 mA/cm² corresponds to 8.2 mA/g,or a C-rate of C/20 (that is a charge/discharge time of 20 hours).

The poor electrochemical performance of LiMnPO₄ and LiMn_(y)Fe_(1-y) PO₄has been attributed to their extremely low electronic and ionicconductivities.^(17,18) Many efforts have therefore been undertaken toreduce the particle size to the sub-micrometer scale and coat suchnanoparticles with conducting carbon, in order to diminish electric andLi-diffusion resistances by shortening the distances for electron andlithium transport.

Direct precipitation of LiMnPO₄ from aqueous medium produced particlesdown to about 100 nm, which after ball-milling with acetylene black gavereversible capacities of about 70 mAh/g at C/20.^(17,19,20) Hydrothermalsynthesis of LiMnPO₄ produced platelets of 100-200 nm thickness, whichafter ball-milling with carbon black yielded a reversible capacity of 68mAh/g at a current density of 1.5 mA/g.²¹ Solid-state synthesis ofLiMn_(0.6)Fe_(0.4) by ball-milling followed by in situ carbon coatingthrough pyrolysis of polypropylene produced 100-200 nm particles and aninitial discharge capacity of 143 mAh/g at C/10.²² Sol-gel synthesis ofLiMnPO₄ produced particles of 140-220 nm, which were reduced to 90-130nm by ball-milling with acetylene black and yielded 134 mAh/g atC/10.²³⁻²⁵ Nanoparticles of LiMnPO₄ of 20-100 nm were obtained by apolyol process, which after ball-milling with acetylene black gave acapacity of about 120 mAh/g at C/10.^(26,27) In conclusion good rateperformance, i.e. high capacity at higher C-rates has still not beenreported.

Rate performance is essential for high power applications, such aselectric vehicles. Various physical parameters are expected to beresponsible for poor kinetics and fast aging of Mn-rich LMFP, including:the large lattice mismatch at the interface between lithiated anddelithiated phase; and the Jahn-Teller lattice distortion associatedwith Mn³⁺.^(13,28-33) Indeed, Kope¢ et al.³⁴ reported recently that theMn³⁺-ions in excess of a critical concentration of 60% undergotransition to the low-spin state, which should renders delithiation(charging) very difficult. In addition, first-principles calculations ofthe surface redox potentials of LMP indicate a large difference betweenthe Li redox potential in the (010) surface layers and the bulk, whichcreates a high energy barrier for Li in the bulk to diffuse out of theparticle, which, if correct would render initiation and charging of thematerial impossible.³⁵

It has been demonstrated that the presence of a metal oxide interfacelayer between the LiMnPO₄ material, and the carbon layer improvedelectrochemical performance, and close to theoretical capacity wasobserved at low rates.^(26,27)

In specific, the presence of a manganese oxide interface layer betweenthe LiMnPO₄ material, and the carbon layer improved electrochemicalperformance. The metal oxide interface layer between LiMnPO₄ and carboncan be detected by Raman spectroscopy. A 633 nm exitation wavelength wasused to observe the highest relative intensity of metal oxide bandscompared with phosphate bands. The close resemblance of its peak patternto hausmannite is evident.^(26,27) Lower symmetry and/or presence onlyin a thin layer on the LMP-carbon interface can be also responsible forsome peak broadening and downshifting compared to Hausmannite. Thesharpness of the Mn—O bands in LMP without Mn-oxalate even at lowerlaser power indicates that this manganese oxide has not been generatedby the laser-induced heating.

The manganese oxide layer is shown to be either Mn₃O₄ (haussmanite),β-MnO₂ (pyrolusite), MnO (manganosit), MnOOH (groutit) or Mn1.85O.6H₂O(birnessite).^(26,27) The method to prepare the manganese oxideinterface layer required a ready-made LiMnPO₄ and milled together with acarbon source.^(26,27) In no cases were pre-cursors of LiMnPO₄ andcarbon or a pre-cursor of carbon were milled to form in-situ both theLiMnPO₄ and the manganese oxide interface layer between the LiMnPO₄material, and the carbon layer.

According to the state of the art lithium metal phosphates LiMPO₄ shouldcontain metals M and phosphate PO₄ in stoichiometric ratio M/PO₄=1 inorder to form a pure single phase material. Any deviations from nominalstoichiometry generally result in the formation of undesirable impurityphases.

DESCRIPTION OF THE INVENTION

The invention relates to a new nanocomposite of lithium manganesephosphate, and a process for manufacturing such a nanocomposite, asdefined in the independent claims.

Preferred embodiments of the invention are defined in the dependentclaims.

According to the present invention good capacity even at high C-rate isobtained with a nanocomposite of lithium manganese phosphate withgeneral formula Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)/C where M is at least oneother metal (e.g. Fe, Ni, Co, Cr, V, Mg, Ca, Al, B, Zn, Cu, Nb, Ti, Zr,La, Ce, Y) and x=0.8-1.1 and y=0.5-1.0 and z=0.9<z<1.1 with a carboncontent of 0.5 to 20% by weight. Part of the oxygen atoms O may besubstituted by fluorine F or part of the phosphate ions PO₄ ³⁻ may besubstituted by silicate ions SiO₄ ⁴⁻, sulfate ions SO₄ ²⁻, vanadate ionsVO₄ ³⁻ or borate ions BO₃ ³⁻.

The nanocomposite according to the invention is produced by milling ofsuitable precursors of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) withelectro-conductive carbon black having a specific surface area of atleast 80 m²/g, or with activated-carbon having a specific surface areaof at least 200 m²/g, or with graphite having a specific surface area ofat least 9.5 m²/g. The reactive milling can be made under inert orreducing atmosphere or direct under air atmosphere, the rest of oxygenwill be rapidly consumed by the carbon. To avoid oxidation of metalsaddition of antioxidant as vitamins C or a reducing agent can beapplied.

Milling breaks covalent bonds in the carbon material and creates highlyreactive coordinatively unsaturated carbon atoms (dangling bonds) on thecarbon surface with which said precursors can react. Thismechanochemical reaction³⁶⁻³⁸ results in a nanocomposite of saidprecursors and carbon, wherein the size of the different domains can becontrolled by the amount and type of carbon material as well as by theintensity and duration of milling. Thermal treatment leads tocrystallization of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) already at relativelylow temperature due to intimate mixing of the precursors by milling.This low crystallization temperature in combination with the covalentlybound carbon prevents crystal growth and results in the smallnanoparticle size of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) in intimate contactwith conducting carbon required for good rate performance.

Acetylene black has most often been used for the synthesis ofLiMPO₄/carbon composites by milling.^(5-9,13-15,39-43) Acetylene blackhas a BET specific surface area of only about 70 m²/g. Like otherconventional carbon blacks of modest specific surface area, includingVulcan XC 72R it consists of fused spherical primary particles (nodules)of about 10-50 nm diameter with onion-shell structure of concentricgraphene like outer layers, while the core is more amorphous.⁴⁴⁻⁴⁶ Thecompactness and resilience of these nodules renders them ratherresistant against breakdown by milling (FIGS. 24 and 25). Therefore thecarbon nodules mainly make point-contacts with the nanoparticles of theactive material, which results in poor electrochemical performance (FIG.8) due to the very low conductivity of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z).This is different from the less insulating LiFePO₄, where point-contactsbetween small enough particles and carbon black have been reported to besufficient for good performance.⁴⁷ This explains why acetylene blackyields only poor rate performance (FIG. 8).

Conductive carbon blacks with high specific surface area according tothe present invention are for example the furnace blacks Printex® XE 2(Evonik Degussa) with 950 m²/g and fused carbon nodules of about 30 nmdiameter, as well as Black Pearls® 2000 (Cabot) with 1500 m²/g and 15 nmparticle diameter. The much higher specific surface area as compared toacetylene black in spite of the similar nodule size is due to a moreopen, porous structure of these nodules, rendering them much morefragile against milling. Therefore milling not only breaks the chains offused carbon nodules but also disrupts the graphene like shells of thenodules, creating dangling bonds for reaction with theLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) precursors.

Ketjenblack® (Akzo Nobel) is another conductive carbon black of highspecific surface area (600-1400 m²/g). It is obtained as by-product inthe synthesis of ammonia and has a fused broken egg-shell structure,which arises from removal of the inner amorphous part of the carbonblack nodules by partial combustion.^(46,48) These shells of about 20 nmouter diameters have a thickness of a few graphene layers only and thusare easily broken by milling, which results in a intimate large-areacontact with the active material (FIG. 23).

Activated carbons are another class of conductive carbon of highspecific surface area (200-3000 m²/g), examples include Norit® DLC Super50. It is obtained via the reactive removal of the inner amorphous partof the carbon by an activation process, creating a pore network. Thefragile and brittle nature of the porous residual renders it easilybroken by milling, the high surface are results in a intimate large-areacontact with the active material.

Graphitic nano-sheets can also be obtained by milling of graphite.⁴⁹⁻⁶⁰Natural as well as synthetic graphite consists of stacked graphenesheets, which are bound by week van der Waals forces only, and hence areeasily separated by sheer forces during milling. This produces thinnergraphene stacks which are more easily broken within the graphene planesby further milling, creating highly reactive dangling bonds at thefreshly created edges. The milling time can be reduced by using expandedgraphite, in which the graphene sheets have already been partiallyseparated by chemical intercalation and thermal expansion. To reduce themilling time even further multiple or single sheet graphene can also beprepared by oxidation of graphite and subsequent exfoliation.⁶¹

Breaking of carbon-carbon bonds by milling creates highly reactivecoordinatively unsaturated carbon atoms (dangling bonds).⁶²⁻⁶⁵ Thisfreshly created carbon surface can react with the other precursorspresent in the mill.

For the solid state synthesis of LiMnPO₄ by mechanochemical reaction theuse of manganese(II)carbonate, ammonium di-hydrogen-phosphate andlithium carbonate has been reported:^(5-12,16,66)MnCo₃+NH₄H₂PO₄+½Li₂CO₃→LiMnPO₄+NH₃+1.5H₂O+1.5CO₂

According to the present invention the liberation of toxic, corrosiveand flammable NH₃ during milling can be avoided withlithium-di-hydrogen-phosphate:MnCO₃+LiH₂PO₄→LiMnPO₄+H₂O+CO₂

This also reduces the amount of water and carbon dioxide produced by50%. Water as byproduct may be avoided completely by employing lithiummetaphosphate:MnCO₃+LiPO₃→LiMnPO₄+CO₂

Solid solutions with lithium iron phosphate can be obtained with e.g.iron oxalate:yMnCO₃+(1−y)FeC₂O₄.2H₂O+LiH₂PO₄→LiMn_(y)Fe_(1-y)PO₄+(3−2y)H₂O+(3−2y)CO₂

Other lithium metal phosphates and their solid solutions can besynthesized accordingly from the appropriate precursors. Instead ofmetal carbonates or oxalates any other suitable metal source can beused, such as oxides (e.g. MnO, Mn₂O₃, MnO₂, Fe₃O₄, Fe₂O₃), hydroxides,salts with carboxylic acids (e.g. acetates) or hydroxyl carboxylic acids(e.g. glycolates, lactates, citrates, tartrates). Other lithium saltscan be employed instead of LiH₂PO₄ or LiPO₃, such as Li₂O, LiOH orLi₂CO₃. Phosphate ions can also be introduced from phosphoric acid (HPO₃or H₃PO₄), as well as any phosphate salt, as long as the byproducts donot degrade the main product.

The water vapor produced by the mechanochemical reaction candissociatively react with the freshly created carbon surface arisingfrom disruption of carbon-carbon bonds by milling, resulting in ahydroxylation of the coordinatively unsaturated carbon atoms:2carbon-C.+H₂O→carbon-C—OH+carbon-C—H

Subsequently these hydroxyl groups can react with transition metal M=Mnor M or phosphate ions:carbon-C—OH+M²⁺→carbon-C—O-M⁺+H⁺carbon-C—OH+H₂PO₄ ⁻→carbon-C—O—PO₃H⁻+H₂O

The coordinatively unsaturated carbon atoms created by milling can alsoreact directly with the metal salt or phosphate ions:carbon-C.+MCO₃→carbon-C—O-M⁺+CO₂carbon-C.+H₂PO₄ ⁻→carbon-C—O—PO₃H⁻+H⁺

Through these chemical reactions of the Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)precursors with the carbon surface nucleation centers are created forthe growth of covalently bound, amorphous Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)by further mechanochemical reaction. On a carbon of very high specificsurface area (as obtained by milling with high surface area carbon blackor graphite) the amorphous Li_(x)Mn_(y)M_(1-y)(PO₄)_(Z) is very finelydispersed resulting in a nanocomposite of very small particle size aftercrystallization treatment and large-area electric contact withconductive carbon, which is crucial for good rate performance. Covalentbinding of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) to carbon through oxygen bridges(C—O-M or C—O—P) also improves the electric contact of the cathodeactive material with the current collector of the battery, which againis important to achieve high current densities. A stoichiometric excessof transition metal precursor during milling favors formation of a metaloxide bonding layer (C—O-M) between carbon and LiMPO₄, while an excessof phosphate favors bonding by phosphate groups (C—O—P).

The presence of covalent bonds between Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) andcarbon can be shown by different analytical techniques, such as infrared(FTIR) and Raman spectroscopy, or X-ray spectroscopy (e.g. XAFS, XANES,XPS). For example the formation of an intermediate manganese oxidebonding layer by ball-milling of nanocrystalline LiMnPO₄ withKetjenblack® in presence of a small amount of water has been revealed byRaman spectroscopy.²⁷

Due to the intimate mixing of the Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)precursors by milling on the nanometer scale crystallization occursalready at moderate temperature (around 400° C.). The low thermaldiffusivity at such a low crystallization temperature results in theformation of very small nanocrystals. In addition, crystal growth isinhibited by the covalently bound carbon in the nanocomposite, whichreduces the diffusivity even more. Hence aLi_(x)Mn_(y)M_(1-y)(PO₄)_(z)/carbon nanocomposite with nanocrystallineLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) of less than about 100 nm crystallite sizeand intimate contact between nanocrystalline active material andconductive carbon is formed, which is a premise for excellentelectrochemical performance.

The primary particle size of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) in thenanocomposite can be determined by electron microscopy (SEM or TEM). Thecrystallite size of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) can be calculated fromthe X-ray diffraction line broadening with the Scherrer equation, ormore accurately with the Warren-Averbach method or by Rietveldrefinement, in order to take into account the contribution of latticestrain to line broadening.

The relative mass of carbon required to obtain an average carbon coatingthickness t on spherical lithium metal phosphate particles of averageradius r is given by:M _(carbon) /M _(LiMPO4)=ρ_(carbon)/ρ_(LiMPO4)·[(1+t/r)³−1]

For r=20 nm and t=1 nm with ρ_(carbon)=2.2 g/cm³ and ρ_(LiMPO4)=3.5g/cm³:M _(carbon) /M _(LiMPO4)=0.1

Hence for spherical Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) particles of 40 nmaverage diameter and a continuous dense carbon coating of 1 nm meanthickness 10 wt % carbon with respect to the mass ofLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) would be required. The necessary amountwould be higher for non-spherical particles since a sphere has thesmallest surface area for a given volume. It would be lower for biggerLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) particles or a thinner or discontinuous orless dense carbon coating.

Carbon exhibits higher electric conductivity when being in its graphitemodification (sp² hybridized carbon) and within the two-dimensionalbasal graphene planes. Hence for good electric conductivity of thecarbon network in the nanocomposite a large fraction and sufficientextension of these graphitic domains with sp² carbon is preferred. Sincethe low heat treatment temperature of 350-600° C. is not sufficient tocause any graphitization a high graphene fraction is advantageouslyalready present in the carbon additive before milling. According to thepresent invention this is achieved by employing electro-conductivecarbon black of high surface area, such as Printex® XE 2 (EvonikDegussa), Black Pearls® 2000 (Cabot) or Ketjenblack® (Akzo Nobel),graphite with specific surface area of at least 9.5 m²/g, expandedgraphite, graphene, or activated carbon. The fraction and size of wellconducting graphene domains in the nanocomposite obtained by milling canbe determined by different analytical techniques, such as Ramanspectroscopy (ratio of graphene G-band around 1580 cm⁻¹ and disorderD-band around 1360 cm⁻¹)^(67,68), X-ray and neutron diffraction, as wellas electron microscopy (TEM).

The invention provides an electroactive lithium manganese phosphatematerial (LiMnPO₄) or solid solution Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) (whereM is at least one other metal (e.g. Fe, Ni, Co, Cr, V, Mg, Ca, Al, B,Zn, Cu, Nb, Ti, Zr, La, Ce, Y) and x=0.8-1.1 and y=0.5-1.0 andz=0.9<z<1.1) characterized in that it comprises a Metal oxide layer onthe LiMnPO₄ material, respectively the LiMn_(y)M_(x1-y)PO₄ material. Theoxide described above is between the LiMnPO₄ material, respectively theLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) material, and a conductive additive such ascarbon. The presence of the oxide layer is demonstrated by Ramanspectroscopy. In contrast to other methods to prepare manganese oxideinterface layer between the Li_(x)Mn_(y)M_(1-y)(PO₄)_(z) material, andthe carbon layer, this novel method prepares both theLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) material and the interface layer in-situfrom precursors of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z).

It has been demonstrated that the presence of a manganese oxideinterface layer between the LiMnPO₄ material, and the carbon layerimproved electrochemical performance. The manganese oxide layer is shownto be either Mn₃O₄ (haussmanite), β-MnO₂ (pyrolusite), MnO (manganosit),MnOOH (groutit) or Mn1.85O.6H₂O (birnessite). The method to prepare themanganese oxide interface layer required a ready-made LiMnPO₄ and milledit with a carbon source. In no cases were pre-cursors of LiMnPO₄ andcarbon milled to form in-situ both the LiMnPO₄ and the manganese oxideinterface layer between the LiMnPO₄ material, and the carbon layer.

According to the state of the art lithium metal phosphates LiMPO₄ shouldcontain metals M and phosphate PO₄ in stoichiometric ratio M/PO₄=1 inorder to form a pure single phase material. Any deviations from nominalstoichiometry generally result in the formation of impurity phases thatdiminish electrochemical performance.

Surprisingly we found that significant stoichiometric excess 1-10% ofphosphate can be accommodated in the case of nanocrystalline LiMPO₄without loss in performance. This is achieved, by for example adding astoichiometric excess of LiH₂PO₄ as a reactant. Due to the very highspecific surface area of nanocrystalline LiMPO₄ excess phosphate isincorporated into the crystal surface and forms a phosphate terminatedsurface. Such a phosphate termination can offer several advantages(FIGS. 15 to 17):

1. Phosphate termination favours formation of strong bonds betweencarbon coating and lithium metal phosphate: this results in betteradhesion and electric contact.

2. Phosphate termination protects the metal ions Mn and M from oxidationduring handling of the material in air.

3. Phosphate termination prevents exposure of the metal ions Mn and M tothe electrolyte and thus their dissolution and subsequent reduction atthe anode, which results in enhanced stability at elevated temperature.

4. Phosphate termination reduces catalytic oxidation of the electrolyteby avoiding direct contact with the transition metal ions Mn and M,which improves stability at high voltage and temperature.

Calculation of Phosphate Excess:

The molar phosphate excess required for complete phosphate terminationof a spherical lithium metal phosphate particle of radius r can becalculated from basic geometry as

$\frac{n_{surface}}{n_{volume}} = {\frac{3}{r} \cdot \sqrt[3]{\frac{M}{\rho \cdot N_{A}}}}$withn_(surface)=average number of lithium metal phosphate formula units inthe particle surfacen_(volume)=number of lithium metal phosphate formula units in theparticle volumer=particle radiusM=molar mass of lithium metal phosphateρ=density of particleN_(A)=Avogadro's number

For example in the case of a spherical LiMn_(0.8)Fe_(0.2)PO₄nanoparticle of 50 nm diameter: r=25 nm, M=158 g/mol, ρ+3.4 g/cm² givesn_(surface)/n_(volume)=0.05

Hence a phosphate excess of 5 mol % would be necessary for completephosphate termination of this nanoparticle.

Since the real lithium metal phosphate powder consists of non-sphericalparticles with a distribution of sizes this is only an approximation.The optimum phosphate excess has to be determined experimentally. Toolow phosphate excess results in partial phosphate termination where partof the transition metal ions remain exposed at the surface (FIG. 15 b).This will not offer the full advantages of a complete phosphatetermination (FIG. 15 c). On the other hand too large phosphate excesswill form a thicker layer with diphosphate (FIG. 15 d) or higherphosphate oligomers on the particle surface. This impedes both electronexchange with the carbon coating and lithium exchange with theelectrolyte and thereby degrades battery performance at high charge ordischarge rate.

FIG. 18 shows the electrochemical performance of a lithium battery withLi_(1.04)Mn_(0.8)Fe_(0.2)(PO₄)_(1.04)/10% C nanocomposite containing 4%excess lithium phosphate (Example 7).

Increasing the phosphate excess in the material to 10% results in theappearance of new crystalline phases, such as Li₂P₂O₇ and otherpolyphosphates, which can be detected by X-ray diffraction (FIG. 19).These new crystalline phases may have benefits including improvedelectrochemical stability, but may have a reduced electrochemicalcapacity.

EXAMPLES Example 1 Synthesis of LiMnPO₄/C nanocomposite

A mixture of 3.45 g MnCO₃ (Aldrich 99.9%)+3.12 g LiH₂PO₄ (Aldrich 99%)+1g Ketjenblack® EC600JD (Akzo Nobel) was milled in a hardened steelcontainer of 250 mL capacity with 12 hardened steel balls of 20 mmdiameter in a planetary ball mill (Retsch PM 100) at 500 rpm for 2hours. The obtained powder was heated up to 450° C. within 30 minutesand maintained at this temperature for 1 hour under a stream of argon+8%hydrogen.

Example 2 Synthesis of LiMn_(0.9)Fe_(0.1)PO₄/C nanocomposite (18%Ketjenblack®)

A mixture of 3.105 g MnCO₃ (Aldrich 99.9%)+0.54 g FeC₂O₄.2H₂O (Fluka99%)+3.12 g LiH₂PO₄ (Aldrich 99%)+1 g Ketjenblack® EC600JD was milled asdescribed in Example 1 and heated at 350, 450 or 550° C. for 1 hourunder argon+8% hydrogen.

FIG. 1 shows a scanning electron microscope picture of the nanocompositeobtained at 450° C., indicating a primary particle size in the order of50 nm for the brighter LiMn_(0.9)Fe_(0.1)PO₄ component.

FIG. 2 shows the X-ray diffraction patterns of the three samples,indicating poor crystallization after 1 hour at 350° C., while thesample heated for the same time at 450° C. is well crystallizedLiMn_(0.9)Fe_(0.1)PO₄ without any apparent impurities. From the linebroadening an average crystallite size of 60 nm with negligible strainwas calculated with the Warren-Averbach method. This agrees with theprimary particle size in the order of 50 nm observed in the SEM picture(FIG. 1).

TABLE 1 LiMn_(0.8)Fe_(0.2)PO₄/ Lattice 10% KetjenblackLiMn_(0.8)Fe_(0.2)PO₄ Reference Reference parameters EC600JD (Yamada2001) LiMnPO₄ LiFePO₄ a 10.419 Å 10.44 Å 10.446 Å 10.34 Å b  6.079 Å 6.09 Å  6.103 Å  6.01 Å c  4.731 Å 4.736 Å  4.744 Å 4.692 Å V 299.70 Å³301.6 Å³ 302.44 Å³ 291.6 Å³

Example 3 Synthesis of LiMn_(0.8)Fe_(0.2)PO₄/10% C Nanocomposites withDifferent Carbon Materials

A mixture of 2.76 g MnCO₃ (Aldrich 99.9%)+1.08 g FeC₂O₄.2H₂O (Fluka99%)+3.12 g LiH₂PO₄ (Aldrich 99%)+0.5 g carbon was milled and heattreated as described in Example 1.

Following carbon materials were compared:

Ketjenblack® EC-300J (Akzo Nobel, 800 m²/g)

Ketjenblack® EC-600JD (Akzo Nobel, 1400 m²/g)

Printex®. XE 2 (Degussa, 950 m²/g)

Black Pearls® 2000(Cabot, 1500 m²/g)

Shawinigan acetylene black C-55 (70 m²/g)

Vulcan XC 72R (270 m²/g)

Multi walled carbon nanotubes (MWCNT)

High surface graphite Timrex® HSAG300 (Timcal, 280 m²/g)

Timrex® KS4 graphite (Timcal, 26 m²/g)

Timrex® KS6 graphite (Timcal, 20 m²/g)

Timrex® SFG6 graphite (Timcal, 17 m²/g)

Timrex® MB15 graphite (Timcal, 9.5 m²/g)

Norit® DLC Super 50 activated carbon (Norit, 1600 m²/g)

Example 4 Synthesis of LiMn_(0.8)Fe_(0.2)PO₄/10% C Nanocomposites with aCombination of Carbon Materials

A mixture of 5.52 g MnCO₃ (Aldrich 99.9%)+2.16 g FeC₂O₄.2H₂O (Fluka99%)+6.24 g LiH₂PO₄ (Aldrich 99%)+0.8 g Cellulose (Aldrich,microcrystalline)+0.4 g Ketjenblack®EC600JD (Akzo Nobel)+0.4 g Timrex®SFG 44 graphite (Timcal) was milled in a hardened steel container of 250mL capacity with 12 hardened steel balls of 20 mm diameter in aplanetary ball mill (Retsch PM 100) at 500 rpm for 2 hours. The obtainedpowder was heated up to 600° C. within 10 minutes and maintained at thistemperature for 20 minutes under a stream of argon.

Example 5 Synthesis of LiMn_(0.9)V_(0.05)(PO₄)_(0.9)(VO₄)_(0.05)/10% CNanocomposite

A mixture of 6.21 g MnCO₃ (Aldrich 99.9%)+0.636 g LiVO₃ (Alfa Aesar99.9%)+5.62 g LiH₂PO₄ (Aldrich 99%)+1 g Ketjenblack® EC600JD was milledin a hardened steel container of 250 mL capacity with 12 hardened steelballs of 20 mm diameter in a planetary ball mill (Retsch PM 100) at 400rpm for 2 hours. The obtained powder was heated up to 500° C. within 10minutes and maintained at this temperature for 20 minutes under a streamof argon.

Example 6 Synthesis of LiMn_(0.9)Ti_(0.1)PO₄/10% C Nanocomposite

A mixture of 6.21 g MnCO₃ (Aldrich 99.9%)+1.77 g (NH₄)₂TiO(C₂O₄)₂.H₂O(Aldrich 99.998%)+6.24 g LiH₂PO₄ (Aldrich 99%)+1 g Ketjenblack® EC600JDwas milled in a hardened steel container of 250 mL capacity with 12hardened steel balls of 20 mm diameter in a planetary ball mill (RetschPM 100) at 400 rpm for 2 hours. The obtained powder was heated up to500° C. within 10 minutes and maintained at this temperature for 20minutes under a stream of argon.

Example 7 Synthesis of Li_(1.04)Mn_(0.8)Fe_(0.2)(PO₄)_(1.04)/10% CNanocomposites with 4% Excess Lithium Phosphate

A mixture of 2.62 g MnCO₃ (Aldrich 99.9%)+1.08 g FeC₂O₄.2H₂O (Fluka99%)+3.12 g LiH₂PO₄ (Aldrich 99%)+0.5 g Timrex SFG 6L graphite (Timcal)was milled and heat treated as described in Example 1.

FIG. 21. trace c and d show the Raman spectra of samples prepared with 5and 10% excess of LiH₂PO₄ described in Experiment 7 respectively. Theyare compared to an equivalent material prepared with no phosphate excess(curve b) as per in example 3). Excitation wavelength 633 nm The changein spectra versus curve b example 3 is illustrative of a differentinterface.

Example 8 Preparation of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)/C Cathodes andSecondary Lithium Batteries with Such Cathodes

1 g of LiMn_(y)Fe_(1-y)PO₄/C nanocomposite as obtained in the aboveExamples was mixed with 20 mg carbon nano fibers (CNF) and 75 mg PVdF(polyvinylidene difluoride) in NMP (N-methyl-2-pyrrolidinon). Thisdispersion was doctor bladed on a carbon coated aluminum foil and driedat 120° C. under vacuum. The electrodes were compressed into Ø 23 mmdisks with a thickness of about 30 μm and an active material loading ofabout 3.0 mg/cm². Cells were assembled in Swagelok™ fittings using Limetal foil as counter electrode with a microporous polymer separator(Celgard 2400™) and an electrolyte of 1M LiPF₆ in ethylene carbonate(EC) and dimethyl carbonate (DMC) 1:1 (by volume)+1% VC.

The electrochemical properties of the LiMn_(y)Fe_(1-y)PO₄/C electrodeswere measured by galvanostatic charge/discharge and cyclic voltammetrywith Arbin BT 2000. FIGS. 3, 5, 7 and 8 show the electrochemicalperformance at different discharging rates. FIGS. 4 and 6 show thestability on cycling at a charge/discharge rate of 1 C.

Example 9

Pure LMP/carbon was prepared by solid state reaction.

A mixture of 3.45 g MnCO3 (Aldrich 99.9%)+3.12 g LiH2PO4 (Aldrich 99%)+1g Ketjenblack® EC600JD (Akzo Nobel) was milled in a hardened steelcontainer of 250 mL capacity with 12 hardened steel balls of 20 mmdiameter in a planetary ball mill (Retsch PM 100) at 500 rpm for 2hours. The obtained powder was heated up to 450° C. within 30 minutesand maintained at this temperature for 1 hour under a stream of argon+8%hydrogen. Alternatively 20% of MnCO3 was exchanged with Mn-oxalate.

FIG. 20 shows the spectra (Labram HR, Horiba Jobin-Yvon, λ=633 nm) ofpure LMP/carbon prepared by solid state reaction as described in example9, in one case with 20% of Mn-oxalate (curve e and f), in the other casewithout Mn-oxalate (curve c and d). In each case, two laser powers areused (D0.6 means higher laser power). For comparison, spectra ofhausmannite Mn3O4 (b) and also MnO2 (a).

In all LMP spectra, the band at ca 645 cm⁻¹ is present. It has thehighest relative intensity in LMP without Mn-oxalate taken at lowerlaser power. The same sample measured at a higher laser power showsrelatively weak signal of Mn3O4. The sample prepared with 20% ofMn-oxalate shows very similar spectra under both laser powers. Theparameters of the possible Mn—O bands in the sample without Mn-oxalateat lower laser power (spectrum d in FIG. 20) are very close to those ofhausmannite in terms of position and FWHM. In the other LMP spectra,these bands are more downshifted and broadened, towards “MnO2” spectrum.

The close resemblance of its peak pattern to hausmannite is evident,albeit not unambiguous. Lower symmetry and/or presence only in a thinlayer on the LMP-carbon interface can be also responsible for some peakbroadening and downshifting compared to hausmannite. The sharpness ofthe Mn—O bands in LMP without Mn-oxalate even at lower laser powerindicates that this manganese oxide has not been generated by thelaser-induced heating.

A partial presence of another Mn-oxide, e.g. bixbyite, (Mn,Fe)2O3,cannot be ruled out. The loss of Mn—O signal with increasing laser powerin this sample (without Mn-oxalate) is intriguing, as well as almost thesame signal in the other sample (with Mn-oxalate) at both laser powers.

Example 10

A mixture of 2.76 g MnCO₃ (Aldrich 99.9%)+1.08 g FeC₂O₄.2H₂O (Fluka99%)+3.12 g LiH₂PO₄ (Aldrich 99%)+0.5 g Ketjenblack® EC600JD was milledas described in Example 1 and heated at 450° C. for 1 hour underargon/H2 atmosphere. A comparative experiment was prepared with the sameconditions, except that the same amount of Vulcan XC72R or Shawiniganacetylene black C-55 was used in place of Ketjenblack® EC600JD (AkzoNobel)

The characterization data and the electrochemical performance are givenin Table 2. The electrochemical performance of cathode material preparedwith Ketjenblack® EC600JD (Akzo Nobel) is close to theoretical value,whereas the cathode material prepared with Shawinigan acetylene blackC-55 show lower electrochemical performance and the material preparedwith Vulcan XC72-R is electrochemical inactive.

In FIG. 22 show Raman spectra of these three cathode materials. TheLiMn_(y)Fe_(1-y)PO₄/C cathode material prepared with Ketjenblack®EC600JD (Akzo Nobel) show the most intensive hausmannite signal at about650 nm, while the material LiMn_(y)Fe_(1-y)PO₄/C prepared with VulcanXC72R does not contain this signal.

TABLE 2 Characterization and electrochemical performance ofLiMn_(y)Fe_(1-y)PO₄/C cathode material prepared with Ketjenblack 600,Acetylene black C55 and Vulcan 72R respectively Carbon Sample Cryst.Capacity LiMn0.8Fe0.2PO4 + BET BET size @ 1 C Sample 10% carbon: m2/gm2/g a/Å b/Å c/Å V/Å3 nm (mAh/g) v150208 Ketjenblack EC-600JD 1400 8810.420 6.081 4.736 300.2 51 132 f26020 acetylene black C-55 70 35 10.4166.073 4.733 299.4 52 99 g150208 Vulcan XC 72R 270 46 10.424 6.081 4.736300.2 47 0

The figures are discussed in more detailed manner below:

FIG. 1 a shows a high resolution scanning electron microscope (HRSEM)picture of the LiMn_(0.9)Fe_(0.1)PO₄/C nanocomposite (18% KetjenblackEC600JD) according to Example 2 after heating for 1 hour under argon/8%hydrogen at 450° C. The primary particle size is in the order of 50 nmfor the brighter LiMn_(0.9)Fe_(0.1)PO₄ component.

FIG. 1 b shows a HRSEM picture of the LiMn_(0.8)Fe_(0.2)PO₄/Cnanocomposite (10% Ketjenblack EC600JD) according to Example 3.

FIG. 1 c shows a TEM picture of the LiMn_(0.8)Fe_(0.2)PO₄/Cnanocomposite (10% Ketjenblack EC600JD) according to Example 3.

FIG. 2 a shows the X-ray diffraction (XRD) patterns of theLiMn_(0.9)Fe_(0.1)PO₄/C nanocomposite (18% Ketjenblack EC600JD)according to Example 2 after heating for 1 hour under argon/8% hydrogenat different temperatures. Only weak XRD peaks are observed after 1 hourat 350° C. indicating poor crystallization, while the sample heated forthe same time at 450° C. is well crystallized LiMn_(0.9)Fe_(0.1)PO₄without any apparent impurities. Heating at 550° C. leads to a furtherincrease in the peak intensities and slight reduction in the peakwidths. From the line broadening at 450° C. an average crystallite sizeof 60 nm with negligible strain was calculated with the Warren-Averbachmethod. This agrees with the primary particle size in the order of 50 nmobserved in the SEM picture (FIG. 1).

FIG. 2 b shows the XRD pattern of the LiMn_(0.8)Fe_(0.2)PO₄/Cnanocomposite (10% Ketjenblack EC600JD)) with Rietveld refinementaccording to Example 3 and Table 1 the crystal data from the XRDpattern.

Mean crystallite size from XRD line broadening L=51 nm

BET surface area A=88 m²/g

FIG. 3 represents the electrochemical performance of two differentlithium batteries with LiMn_(0.9)Fe_(0.1)PO₄/C nanocomposite cathode(18% Ketjenblack EC600JD, Example 2) at different discharge rates oncycling between 2.7 and 4.4 V against lithium. A capacity of 150 mAh/gof active material is achieved at D/10. Even at a discharge rate of 5D acapacity as high as 130 mAh/g is obtained.

FIG. 4 shows the cycling stability (at 1 C and C/10 each 10th cycle,charged up to 4.25 V) of the lithium batteries from FIG. 3 withLiMn_(0.9)Fe_(0.1)PO₄/C nanocomposite cathode (18% Ketjenblack EC600JD,Example 2).

FIG. 5 shows the electrochemical performance of a lithium battery withLiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite cathode (10% Ketjenblack EC600JD,Example 3) at different discharge rates on cycling between 2.7 and 4.4 Vagainst lithium. A capacity of 145 mAh/g of active material is obtainedat D/10. At a discharge rate of 5D the capacity is still higher than 110mAh/g.

FIG. 6 a shows the cycling stability at 21° C. (discharge rate 1 C andC/10 each 10th cycle, charged up to 4.25 V) of a lithium batteryaccording to FIG. 5 with LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite cathode(10% Ketjenblack EC600JD, Example 3).

Charging condition: CCCV 2.7-4.25V vs. Li

Discharge: C rate calculated from 150 mAh/g

Cathode: LiMn_(0.8)Fe_(0.2)PO₄/C+2% CNF+7.5% PVDF

Loading: 2.7 mg/cm²

Electrolyte: LP30+1% VC

FIG. 6 b shows the cycling stability at 50° C. (discharge rate 5 C,charged up to 4.25 V) of a lithium battery according to FIG. 5 withLiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite cathode (10% Ketjenblack EC600JD,Example 3).

Charging condition: CCCV 2.7-4.25V vs. Li

Discharge: C rate calculated from 150 mAh/g

Cathode: LiMn_(0.8)Fe_(0.2)PO₄/C+2% CNF+7.5% PVDF

Loading: 5.4 mg/cm²

Electrolyte: LP30+1% VC

FIG. 7 shows the electrochemical performance of lithium batteries withLiMn_(0.8)Fe_(0.2)PO₄/10% C nanocomposite cathodes prepared fromdifferent carbon sources (Example 3) on cycling between 2.7 and 4.4 Vagainst lithium:

Δ Ketjenblack EC-300J (Akzo Nobel, 800 m²/g)

□ Ketjenblack EC-600JD (Akzo Nobel, 1400 m²/g)

▴ Black Pearls 2000 (Cabot, 1500 m²/g)

♦ Multi walled carbon nanotubes (MWCNT)

▪ High surface graphite Timrex HSAG300 (Timcal, 280 m²/g)

Ketjenblack EC-600JD and high surface graphite Timrex HSAG300 show thebest performance with a capacity of 145 mAh/g at D/10 and more than 110mAh/g at 5D.

FIG. 8 shows the electrochemical performance of lithium batteries withLiMn_(0.8)Fe_(0.2)PO₄/10% C nanocomposite cathodes prepared fromdifferent carbon sources (Example 3) on cycling between 2.7 and 4.4 Vagainst lithium:

▴ Ketjenblack EC-600JD (Akzo Nobel, 1400 m²/g)

♦ Timrex KS4 graphite (Timcal, 26 m²/g)

⋄ Timrex SFG6 graphite (Timcal, 17 m²/g)

□ Timrex MB15 graphite (Timcal, 9.5 m²/g)

Δ A Shawinigan acetylene black C-55 (70 m²/g)

The three different graphites yield comparable performance toKetjenblack EC-600JD. Shawinigan acetylene black C-55 gives much lowercapacity, especially at higher discharge rates.

FIG. 9

Raman spectra of pure carbons and LiMn_(0.8)Fe_(0.2)PO₄/10% carbonnanocomposites (Example 3) in the region of the graphitic G band around1600 cm⁻¹ and the disordered carbon D band around 1350 cm⁻¹.

The carbons are:

KB600: Ketjenblack EC600JD (Akzo Nobel, 1400 m²/g)

KB300: Ketjenblack EC300J (Akzo Nobel, 800 m²/g)

C55: Shawinigan acetylene black (70 m²/g)

KS6: Timrex graphite (Timcal, 20 m²/g)

FIG. 10

Cyclic voltammogram of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite cathode(10% Ketjenblack EC600JD, Example 3)

FIG. 11

Discharge curves of a lithium battery with LiMn_(0.8)Fe_(0.2)PO₄/Cnanocomposite cathode (10% Ketjenblack EC600JD, Example 3) at 21° C.

Charging condition: CCCV 2.7-4.4 V vs. Li

Discharge: C rate calculated from 150 mAh/g

Electrode: LiMn_(0.8)Fe_(0.2)PO₄/C+2% CNF+7.5% PVDF

Loading: 4.6 mg/cm²

Electrolyte: 1M LiPF₆/EC/DMC 1:1+2% VC

FIG. 12

Discharge curves of a lithium battery with LiMn_(0.8)Fe_(0.2)PO₄/Cnanocomposite cathode (10% Ketjenblack EC600JD, Example 3) at 50° C.

Charging condition: CCCV 2.7-4.4 V vs. Li

Discharge: C rate calculated from 150 mAh/g

Electrode: LiMn_(0.8)Fe_(0.2)PO₄/C+2% CNF+7.5% PVDF

Loading: 4.4 mg/cm²

Electrolyte: 1M LiPF₆/EC/DMC 1:1+1% VC

FIG. 13

Cell charge status for XRD analysis

Electrode from coin cell

0.1 C for 2˜3 cycles

2.0V: 0.01 C discharge and CV to 2.0V→Li_(≈1)Mn_(0.8)Fe_(0.2)PO₄

3.4V: 0.1 C charge and CV to 3.4V→Li_(≈0.95)Mn_(0.8)Fe_(0.2)PO₄

4.0V: 0.1 C charge and CV to 4.0V→Li_(≈0.7)Mn_(0.8)Fe_(0.2)PO₄

4.4V: 0.1 C charge and CV to 4.4V→Li_(≈0)Mn_(0.8)Fe_(0.2)PO₄

After CV, dismount the coin cell and clean with EMC then dry in vacuumoven with 60° C.

FIG. 14

XRD patterns of the cathode at different states of charge

2.0V→Li_(≈1)Mn_(0.8)Fe_(0.2)PO₄

3.4V→Li_(≈0.95)Mn_(0.8)Fe_(0.2)PO₄

4.0V→Li_(≈0.7)Mn_(0.8)Fe_(0.2)PO₄, still single olivine phase withreduced lattice parameters

4.4V→Li_(≈0)Mn_(0.8)Fe_(0.2)PO₄, new phase

FIG. 15

Schematic side view of the lithium metal phosphate particle surface withdifferent terminations (the charge compensating lithium ions are omittedfor clarity)

FIG. 16

Simplified two-dimensional representation of the lithium metal phosphatelattice with a) stoichiometric surface and b) the same surface withphosphate termination (in the real three-dimensional lattice the metalions M have octahedral coordination).

FIG. 17

Simplified two-dimensional representation of the lithium metal phosphatelattice with a) metal hydroxide terminated surface and b) the samesurface with phosphate termination (in the real three-dimensionallattice the metal ions M have octahedral coordination).

FIG. 18 shows the electrochemical performance of a lithium battery withLi_(1.04)Mn_(0.8)Fe_(0.2)(PO₄)_(1.04)/10% C nanocomposite containing 4%excess lithium phosphate (Example 7).

FIG. 19 shows the XRD patterns of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposites(10% Ketjenblack EC600JD) with stoichiometric composition and 5%,respectively 10% excess LiH₂PO₄

FIG. 20 show the Raman spectra of pure LiMnPO₄+carbon prepared asdescribed in example 9, in one case with 20% of Mn-oxalate (curve e andf), in the other case without Mn-oxalate (curve c and d), together withMnO₂ (curve a) and hausmannite Mn₃O₄ from Aldrich (curve b). Spectrum(c) is LMP without Mn-oxalate, sample F101_B_(—)5. Spectrum (d) is LMPwithout Mn-oxalate, sample F101_B_(—)6. Spectrum (e) is LMP withMn-oxalate, sample F101_A_(—)4. Spectrum (f) is LMP with Mn-oxalate,sample F101_A_(—)5. In each case, two laser powers are used (D0.6 meanshigher laser power). Excitation wavelength 633 nm. The spectra areoffset for clarity. The spectra are normalized to the intensity of the□₁(PO₄) band (in the case of LMP samples).

Both the measured manganese oxides (curve a and b) are characterized byan intense band at around 640-650 cm-1, and a few less intense bandsbetween 300 and 500 cm-1. In the case of MnO2, all the bands are verybroad and downshifted. Moreover, some other bands are present, e.g. at520 cm-1. The explanation for the similarity is based upon the higheststability against the laser of hausmannite amongst manganese oxides.Therefore, some of other manganese oxides tend to verge into Mn3O4during the Raman observation. In all LMP spectra, the band at ca 645cm-1. It has the highest relative intensity in LMP without Mn-oxalatetaken at lower laser power. On the other hand, the same sample measuredat a higher laser power shows relatively weak signal of Mn3O4. Thesample prepared with 20% of Mn-oxalate shows very similar spectra underboth laser powers. The parameters of the possible Mn—O bands in thesample without Mn-oxalate at lower laser power (spectrum d in FIG. 20)are very close to those of hausmannite in terms of position and FWHM. Inthe other LMP spectra, these bands are more downshifted and broadened,towards “MnO2” spectrum. The close resemblance of its peak pattern tohausmannite is evident, albeit not unambiguous. Lower symmetry and/orpresence only in a thin layer on the LMP-carbon interface can be alsoresponsible for some peak broadening and downshifting compared tohausmannite. The sharpness of the Mn—O bands in LMP without Mn-oxalateeven at lower laser power indicates that this manganese oxide has notbeen generated by the laser-induced heating.

A partial presence of another Mn-oxide, e.g. bixbyite, (Mn,Fe)2O3,cannot be ruled out. The loss of Mn—O signal with increasing laser powerin this sample (without Mn-oxalate) is intriguing, as well as almost thesame signal in the other sample (with Mn-oxalate) at both laser powers.

FIG. 21 shows the spectra (Labram HR, Horiba Jobin-Yvon, λ 633 nm) ofLMP/LFP/carbon mixtures prepared as described in Example 2 and Example7, comparing two Calcination conditions which may lead to differentamounts of oxidation interface. Calcination in pure argon (curve Asample HPLLMP66) vs. argon/hydrogen (curve B, sample HPLLMP67). However,it was not possible to measure the two samples under the same laserpower. HPLLMP66 (under Ar—Curve A) gave no signal besides carbon at D2,while HPLLMP67 (under Ar/H2—curve B showed optical changes (i.e.burning) during irradiation at D1. Though one accumulation spectrum atD1 was roughly similar to that at D2, a longer exposition to acquire abetter quality spectrum was not possible. Such a varying reaction to thelaser already points to a different nature of the Ar and Ar/H2 calcinedmaterials and their interfaces.

The observed broadening of the bands in HPLLMP66 curve A is caused bythe higher laser power. A slightly higher Fe2O3 signal in this sampleand significantly more intense ν4(PO4) band at 625 cm-1 in curve B,HPLLMP67 (Ar/H2) point to a more reduced state of sample calcined underAr/H2) and a more oxidized state of the sample calcined only underargon, which was anticipated. This is indicative of a modifiedinterface.

The curve c and d in FIG. 21 show LMP/LFP/carbon mixtures prepared with5 and 10% excess of LiH2PO4, respectively (same laser power) they areprepared as in Example 7. In this samples is the Fe2O3 and Mn3O4 signalsless intensive but still obvious. The ν1(PO4) band is also narrower by1.5 cm-1 for 10% LiH2PO4 excess sample. The change in spectra versuscurve b example 3 is illustrative of a different interface.

FIG. 22 shows Raman spectra of LiMn_(y)Fe_(1-y)PO₄/C cathode materialprepared in example 3 with Ketjenblack® EC600JD (Akzo Nobel)LiMn_(y)Fe_(1-y)PO₄/C, Vulcan XC72R and Acetylene black C55 measuredusing LabRam HR, Horiba JY. The laser excitation wavelength was 633 nmand spectra are normalized to the ν₁ PO₄ vibration at 945 cm⁻¹.

FIG. 23

HRTEM picture of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite with 10%Ketjenblack® EC-600JD (Akzo Nobel, 1400 m²/g) (Example 3) showingintimate large-area contact between carbon and nanocrystalline activematerial (lattice fringes).

FIG. 24

HRTEM picture of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite with 10%Shawinigan acetylene black C-55 (70 m²/g) (Example 3) showing intactcarbon black onions making only point contacts with prismaticnanocrystals of active material.

FIG. 25

HRTEM picture of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite with 10%Shawinigan acetylene black C-55 (70 m²/g) (Example 3) showing a carbononion and a nanocrystal of active material (lattice fringes) withoutcarbon coating.

FIG. 26

HRTEM picture of LiMn_(0.8)Fe_(0.2)PO₄/C nanocomposite with 10% VulcanXC 72R (270 m²/g) (Example 3) showing intact carbon onions.

REFERENCES

-   1. Howard, W. F.; Spotnitz, R. M., Theoretical evaluation of    high-energy lithium metal phosphate cathode materials in Li-ion    batteries. Journal of Power Sources 2007, 165, (2), 887-891.    http://dx.doi.org/10.1016/j.jpowsour.2006.12.046-   2. Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B.,    Phospho-olivines as positive-electrode materials for rechargeable    lithium batteries. Journal of the Electrochemical Society 1997, 144,    (4), 1188-1194. http://dx.doi.org/10.1149/1.1837571-   3. Goodenough, J. B., Cathode materials for secondary (rechargeable)    lithium batteries. U.S. Pat. No. 5,910,382 1999.    http://www.google.com/patents?id=RYEZAAAAEBAJ&dq=goodenough-   4. Goodenough, J. B., Cathode materials for secondary (rechargeable)    lithium batteries. U.S. Pat. No. 6,514,640 2003.    http://www.google.com/patents?id=L4NAAAAEBAJ&dg=goodenough-   5. Yamada, A.; Li, G.; Azuma, H., Positive electrode active    material, non-aqueous electrolyte secondary battery. U.S. Pat. No.    7,217,474 2007.    http://www.google.com/patents?id=BPh_AAAAEBAJ&dq=7217474-   6. Yamada, A.; Li, G.; Azuma, H., Positive electrode active    material, non-aqueous electrolyte secondary battery. U.S. Pat. No.    7,147,969 2006.    http://www.google.com/patents?id=oJd9AAAAEBAJ&dq=7147969-   7. Okawa, T.; Hosoya, M.; Kuyama, J.; Fukushima, Y., Non-aqueous    electrolyte secondary cell with a lithium metal phosphate cathode.    U.S. Pat. No. 7,122,272 2006.    http://www.google.com/patents?id=dhh7AAAAEBAJ&dq=7122272-   8. Li, G., Positive electrode material and battery using the same.    U.S. Pat. No. 7,029,795 2006.    www.google.com/patents?id=AoN3AAAAEBAJ&dq=7029795-   9. Li, G., Positive electrode active material and non-aqueous    electrolyte cell. U.S. Pat. No. 6,749,967 2004.    http://www.google.com/patents?id=8fAPAAAAEBAJ&dq=6749967    http://www.freepatentsonline.com/6749967.html-   10. Yamada, A.; Li, G.; Azuma, H., Positive electrode active    material, non-aqueous electrolyte secondary battery. U.S. Pat. No.    6,632,566 2003.    http://www.google.com/patents?id=t58NAAAAEBAJ&dq=Guohua+Li-   11. Li, G. H.; Azuma, H.; Tohda, M., LiMnPO4 as the cathode for    lithium batteries. Electrochemical and Solid State Letters 2002, 5,    (6), A135-A137. http://dx.doi.org/10.1149/1.1475195-   12. Yamada, A.; Chung, S. C., Crystal chemistry of the olivine-type    Li(MnyFe1-y)PO4 and (MnyFe1-y)PO4 as possible 4 V cathode materials    for lithium batteries. Journal of the Electrochemical Society 2001,    148, (8), A960-A967. http://dx.doi.org/10.1149/1.1385377-   13. Yamada, A.; Hosoya, M.; Chung, S. C.; Kudo, Y.; Hinokuma, K.;    Liu, K. Y.; Nishi, Y., Olivine-type cathodes achievements and    problems. Journal of Power Sources 2003, 119, 232-238.    http://dx.doi.org/10.1016/S0378-7753(03)00239-8-   14. Li, G.; Yamada, A.; Azuma, H., Method for manufacturing active    material of positive plate and method for manufacturing nonaqueous    electrolyte secondary cell. EP1094532 2001.-   15. Li, G.; Yamada, A., Positive electrode active material and    non-aqueous electrolyte cell. Patent 2001, US 20010055718.    http://www.freepatentsonline.com/20010055718.html-   16. Li, G. H.; Azuma, H.; Tohda, M., Optimized LiMnyFe1-yPO4 as the    cathode for lithium batteries. Journal of the Electrochemical    Society 2002, 149, (6), A743-A747.    http://dx.doi.org/10.1149/1.1473776-   17. Delacourt, C.; Laffont, L.; Bouchet, R.; Wurm, C.; Leriche, J.    B.; Morcrette, M.; Tarascon, J. M.; Masquelier, C., Toward    understanding of electrical limitations (electronic, ionic) in    LiMPO4 (M=Fe, Mn) electrode materials. Journal of the    Electrochemical Society 2005, 152, A913-A921.    http://dx.doi.org/10.1149/1.1884787-   18. Molenda, J.; Ojczyk, W.; Marzec, J., Electrical conductivity and    reaction with lithium of LiFe1-yMnyPO4 olivine-type cathode    materials. Journal of Power Sources 2007, 174, (2), 689-694.    http://dx.doi.org/10.1016/j.jpowsour.2007.06.238-   19. Delacourt, C.; Poizot, P.; Morcrette, M.; Tarascon, J. M.;    Masquelier, C., One-step low-temperature route for the preparation    of electrochemically active LiMnPO4 powders. Chemistry of Materials    2004, 16, (1), 93-99. http://dx.doi.org/10.1021/cm 030347b-   20. Delacourt, C.; Wurm, C.; Reale, P.; Morcrette, M.; Masquelier,    C., Low temperature preparation of optimized phosphates for    Li-battery applications. Solid State Ionics 2004, 173, (1-4),    113-118. http://dx.doi.org/10.1016/j.ssi.2004.07.061-   21. Fang, H. S.; Li, L. P.; Li, G. S., Hydrothermal synthesis of    electrochemically active LiMnPO4. Chemistry Letters 2007, 36,    436-437. <Go to ISI>://WOS:000246058000043-   22. Mi, C. H.; Zhang, X. G.; Zhao, X. B.; Li, H. L., Synthesis and    performance of LiMn0.6Fe0.4PO4/nano-carbon webs composite cathode.    Materials Science and Engineering B-Solid State Materials for    Advanced Technology 2006, 129, (1-3), 8-13.    http://dx.doi.org/10.1016/j.mseb.2005.11.015-   23. Drezen, T.; Kwon, N.-H.; Bowen, P.; Teerlinck, I.; Isono, M.;    Exnar, I., Effect of particle size on LiMnPO4 cathodes. Journal of    Power Sources 2007, 174, (2), 949-953.    http://dx.doi.org/10.10161/j.jpowsour.2007.06.203-   24. Kwon, N. H.; Drezen, T.; Exnar, I.; Teerlinck, I.; Isono, M.;    Graetzel, M., Enhanced electrochemical performance of    mesoparticulate LiMnPO4 for lithium ion batteries. Electrochemical    and Solid State Letters 2006, 9, (6), A277-A280.    http://dx.doi.org/10.1149/1.2191432-   25. Kwon Roth, N. H., Mesoscopic manganese based cathode materials    for high voltage lithium ion batteries. Ph.D. Thesis, ÉCOLE    POLYTECHNIQUE FÉDÉRALE DE LAUSANNE 2006.    http://library.epfl.ch/theses/?nr=3502-   26. Exnar, I.; Drezen, T., Synthesis of nanoparticles of lithium    metal phosphate positive material for lithium secondary battery.    PCT/IB2006/051061 2006.    http://www.wipo.int/pctdb/en/wo.jsp?wo=2007113624-   27. Exnar, I.; Drezen, T.; Frank; Zukalova; Miners, J.; Kavan, L.,    Carbon Coated Lithium Manganese Phosphate Cathode Material. EPA No.    07112490.3.-   28. Yamada, A.; Kudo, Y.; Liu, K. Y., Reaction mechanism of the    olivine-type Li-x(Mn0.6Fe0.4)PO4 (0<=x<=1). Journal of the    Electrochemical Society 2001, 148, (7), A747-A754.    http://link.aip.org/link/?JES/148/A747/1-   29. Yamada, A.; Chung, S. C., Crystal chemistry of the olivine-type    LiMn_(y)Fe_(1-y)PO₄ and Mn_(y)Fe_(1-y)PO₄ as possible 4 V cathode    materials for lithium batteries. Journal of the Electrochemical    Society 2001, 148, (8), A960-A967.    http://dx.doi.org/10.1149/1.1385377-   30. Yamada, A.; Kudo, Y.; Liu, K. Y., Phase diagram of    Li-x(MnyFe1-y)PO4 (0<=x, y<=1). Journal of the Electrochemical    Society 2001, 148, (10), A1153-A1158.-   31. Yamada, A.; Masao, Y.; Yuki, T.; Noriyuki, S.; Ryoji, K., Fast    Charging LiFePO4. Electrochemical and Solid-State Letters 2005, 8,    (1), A55-A58. http://dx.doi.org/10.1149/1.1836117-   32. Yamada, A.; Takei, Y.; Koizumi, H.; Sonoyama, N.; Kanno, R.;    Itoh, K.; Yonemura, M.; Kamiyama, T., Electrochemical, magnetic, and    structural investigation of the Li-x(MnyFe1-y)PO4 olivine phases.    Chemistry of Materials 2006, 18, (3), 804-813.-   33. Meethong, N.; Huang, H. Y. S.; Speakman, S. A.; Carter, W. C.;    Chiang, Y. M., Strain accommodation during phase transformations in    olivine-based cathodes as a materials selection criterion for    high-power rechargeable batteries. Advanced Functional Materials    2007, 17, 1115-1123.-   34. Kope¢, M.; Yamada, A.; Kobayashi, G.; Nishimura, S.; Kanno, R.;    Mauger, A.; Gendron, F.; Julien, C. M., Structural and magnetic    properties of Lix(MnyFe1-y)PO4 electrode materials for Li-ion    batteries. Journal of Power Sources 2009, In Press, Corrected Proof.    http://dx.doi.org/10.10161/j.jpowsour.2008.12.096-   35. Wang, L.; Zhou, F.; Ceder, G., Ab Initio Study of the Surface    Properties and Nanoscale Effects of LiMnPO[sub 4]. Electrochemical    and Solid-State Letters 2008, 11, (6), A94-A96.    http://link.aip.org/link/?ESL/11/A94/1-   36. Boldyrev, V. V., Mechanochemistry and mechanical activation of    solids. Russian Chemical Reviews 2006, 75, (3), 177-189.    http:/dx.doi.org/10.1070/RC2006v075n03ABEH001205-   37. Suryanarayana, C., Mechanical Alloying and Milling. Marcel    Dekker: New York, 2004.-   38. Tarascon, J. M.; Morcrette, M.; Saint, J.; Aymard, L.; Janot,    R., On the benefits of ball milling within the field of rechargeable    Li-based batteries. Comptes Rendus Chimie 2005, 8, (1), 17-26.    http://dx.doi.org/10.1016/j.crci2004.12.006-   39. Hosoya, M.; Takahashi, K.; Fukushima, Y., Cathode active    material, method for preparation thereof, non-aqueous electrolyte    cell and method for preparation thereof. EP1184920 2002.    http://www.freepatentsonline.com/EP1184920.html-   40. Hosoya, M.; Takahashi, K.; Fukushima, Y., Method for the    preparation of cathode active material and method for the    preparation of a non-aqueous electrolyte cell. EP1193783 2002.    http://www.freepatentsonline.com/EP1193783.html-   41. Hosoya, M.; Takahashi, K.; Fukushima, Y., Method for the    preparation of cathode active material and method for the    preparation of a non-aqueous electrolyte cell. EP1193784 2002.    http://www.freepatentsonline.com/EP1193784.html-   42. Hosoya, M.; Takahashi, K.; Fukushima, Y., Method for the    preparation of cathode active material and method for the    preparation of a non-aqueous electrolyte cell. EP1193786 2007.    http://www.freepatentsonline.com/EP1193786.html-   43. Hosoya, M.; Takahashi, K.; Fukushima, Y., Method for the    preparation of cathode active material and method for the    preparation of a non-aqueous electrolyte cell. EP1193787 2002.    http://www.freepatentsonline.com/EP1193787.html    http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=KR20020025819-   44. Wissler, M., Graphite and carbon powders for electrochemical    applications. Journal of Power Sources 2006, 156, (2), 142-150.    http://www.sciencedirect.com/science/article/B6TH1-4JRVB7F-1/2/a12b20d1243a2f3a9322962574213d5c-   45. Ozawa, M.; Ōsawa, E., Carbon Blacks as the Source Materials for    Carbon, in “Carbon Nanotechnology”, Dai, L. (Ed.), Chapt. 6, p.    127-151, Elsevier: Dordrecht, 2006. 2006.-   46. Tashima, D.; Kurosawatsu, K.; Uota, M.; Karashima, T.; Sung, Y.    M.; Otsubo, M.; Honda, C., Space charge behaviors of electric double    layer capacitors with nanocomposite electrode. Surface & Coatings    Technology 2007, 201, (9-11), 5392-5395.    http://dx.doi.org/10.1016/j.surfcoat.2006.07.045-   47. Gaberscek, M.; Dominko, R.; Jamnik, J., Is small particle size    more important than carbon coating? An example study on LiFePO4    cathodes. Electrochemistry Communications 2007, 9, (12), 2778-2783.-   48. Nelson, J. R.; Wissing, W. K., Morphology of Electrically    Conductive Grades of Carbon-Black. Carbon 1986, 24, (2), 115-121.    http://dx.doi.org/10.1016/0008-6223(86)90104-1-   49. Antisari, M. V.; Montone, A.; Jovic, N.; Piscopiello, E.;    Alvani, C.; Pilloni, L., Low energy pure shear milling: A method for    the preparation of graphite nano-sheets. Scripta Materialia 2006,    55, (11), 1047-1050.    http://dx.doi.org/10.1016/j.seriptamat.2006.08.002-   50. Wong, S. C.; Sutherland, E. M.; Uhl, F. M., Materials processes    of graphite nanostructured composites using ball milling. Materials    and Manufacturing Processes 2006, 21, (2), 159-166.    http://dx.doi.org/10.1081/AMP-200068659-   51. Drofenik, M.; Makovec, D.; Kosak, A.; Kristl, M., Synthesis of    carbon nanostructures with mechanical alloying. Progress in Advanced    Materials and Processes 2004, 453-454, 213-217.    http://scholar.google.com/scholar?hl=en&lr=&cluster=12937135160538548640-   52. Chen, X. H.; Yang, H. S.; Wu, G. T.; Wang, M.; Deng, F. M.;    Zhang, X. B.; Peng, J. C.; Li, W. Z., Generation of curved or    closed-shell carbon nanostructures by ball-milling of graphite.    Journal of Crystal Growth 2000, 218, (1), 57-61.    http://dx.doi.org/10.1016/S0022-0248(00)00486-3-   53. Chen, Y.; Fitz Gerald, J. D.; Chadderton, L. T.; Chaffron, L.,    Nanoporous carbon produced by ball milling. Applied Physics Letters    1999, 74, (19), 2782-2784. http://dx.doi.org/10.1063/1.124012-   54. Huang, J. Y.; Yasuda, H.; Mori, H., Highly curved carbon    nanostructures produced by ball-milling. Chemical Physics Letters    1999, 303, (1-2), 130-134.    http://dx.doi.org/10.1016/S0009-2614(99)00131-1-   55. Harker, H.; Horsley, J. B.; Robson, D., Active Centres Produced    in Graphite by Powdering. Carbon 1971, 9, (1), 1-&.    http://dx.doi.org/10.1016/0008-6223(71)90139-4-   56. Hentsche, M.; Hermann, H.; Gemming, T.; Wendrock, H.; Wetzig,    K., Nanostructured graphite prepared by ball-milling at low    temperatures. Carbon 2006, 44, (4), 812-814.    http://dx.doi.org/10.1016/j.carbon.2005.10.037-   57. Salver-Disma, F.; Tarascon, J. M.; Clinard, C.; Rouzaud, J. N.,    Transmission electron microscopy studies on carbon materials    prepared by mechanical milling. Carbon 1999, 37, (12), 1941-1959.    http://dx.doi.org/10.1016/S0008-6223(99)00059-7-   58. Janot, R.; Guerard, D., Ball-milling: the behavior of graphite    as a function of the dispersal media. Carbon 2002, 40, (15),    2887-2896. http://dx.doi.org/10.1016/S0008-6223(02)0022-3-   59. Ong, T. S.; Yang, H., Effect of atmosphere on the mechanical    milling of natural graphite. Carbon 2000, 38, (15), 2077-2085.    http:/dx.doi.org/10.1016/S0008-6223(00)00064-6-   60. Salver-Disma, F.; Du Pasquier, A.; Tarascon, J. M.;    Lassegues, J. C.; Rouzaud, J. N., Physical characterization of    carbonaceous materials prepared by mechanical grinding. Journal of    Power Sources 1999, 82, 291-295.    http://dx.doi.org/10.1016/S0378-7753(99)00205-0-   61. Geim, A. K.; Novoselov, K. S., The rise of graphene. Nature    Materials 2007, 6, (3), 183-191.-   62. Jiang, D. E.; Sumpter, B. G.; Dai, S., Unique chemical    reactivity of a graphene nanoribbon's zigzag edge. Journal of    Chemical Physics 2007, 126, (13).    http://dx.doi.org/10.1063/1.2715558-   63. Enoki, T.; Kobayashi, Y.; Fukui, K. I., Electronic structures of    graphene edges and nanographene. International Reviews in Physical    Chemistry 2007, 26, 609-645.    http://dx.doi.org/10.1080/01442350701611991-   64. Hermann, H.; Schubert, T.; Gruner, W.; Mattern, N., Structure    and chemical reactivity of ball-milled graphite. Nanostructured    Materials 1997, 8, (2), 215-229.    http://dx.doi.org/10.1016/S0965-9773(97)00010-X-   65. Francke, M.; Hermann, H.; Wenzel, R.; Seifert, G.; Wetzig, K.,    Modification of carbon nanostructures by high energy ball-milling    under argon and hydrogen atmosphere. Carbon 2005, 43, (6),    1204-1212. http://dx.doi.org/10.1016/j.carbon.2004.12.013-   66. Li, G. H.; Kudo, Y.; Liu, K. Y.; Azuma, H.; Tohda, M., X-ray    absorption study of LixMnyFe1-yPO4 (0<=x<=1,0y<=1). Journal of the    Electrochemical Society 2002, 149, (11), A1414-A1418.    http://dx.doi.org/10.1149/1.1510768-   67. Tuinstra, F.; Koenig, J. L., Raman Spectrum of Graphite. Journal    of Chemical Physics 1970, 53, (3), 1126-&.    http://dx.doi.org/10.1063/1.1674108-   68. Nakamizo, M.; Honda, H.; Inagaki, M., Raman spectra of ground    natural graphite. Carbon 1978, 16, (4), 281-283.    http://dx.doi.org/10.1016/0008-6223(78)90043-X

What is claimed is:
 1. A process for the production of a lithiummanganese phosphate/carbon nanocomposite as cathode material forrechargeable electrochemical cells with the general formulaLi_(x)Mn_(y)M_(1-y)(PO₄)_(z)/C where M is at least one other metal suchas Fe, Ni, Co, Cr, V, Mg, Ca, Al, B, Zn, Cu, Nb, Ti, Zr, La, Ce, Y,x=0.8-1.1, y=0.5-1.0, 0.9≦z≦1.1, with a carbon content of 0.5 to 20% byweight, comprising milling of precursors of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)with electro-conductive carbon black having a specific surface area ofat least 80 m²/g or with graphite having a specific surface area of atleast 9.5 m²/g or with activated carbon having a specific surface areaof at least 200 m²/g and heating to form the lithium manganesephosphate/carbon nanocomposite.
 2. A process for the production of alithium manganese phosphate/carbon nanocomposite as cathode material forrechargeable electrochemical cells with the general formulaLi_(x)Mn_(y)M_(1-y)(PO₄)_(z)/C where M is at least one other metal suchas Fe, Ni, Co, Cr, V, Mg, Ca, Al, B, Zn, Cu, Nb, Ti, Zr, La, Ce, Y,x=0.8-1.1, y=0.5-1.0, 0.9≦z≦1.1, with a carbon content of 0.5 to 20% byweight, comprising milling of precursors of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)with electro-conductive carbon black having a specific surface area ofat least 80 m²/g or with graphite having a specific surface area of atleast 9.5 m²/g or with activated carbon having a specific surface areaof at least 200 m²/g and heating to form the lithium manganesephosphate/carbon nanocomposite, wherein a metal precursor for theLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) is added in stoichiometric excess withrespect to a phosphate precursor.
 3. A process for the production of alithium manganese phosphate/carbon nanocomposite as cathode material forrechargeable electrochemical cells with the general formulaLi_(x)Mn_(y)M_(1-y)(PO₄)_(z)/C where M is at least one other metal suchas Fe, Ni, Co, Cr, V, Mg, Ca, Al, B, Zn, Cu, Nb, Ti, Zr, La, Ce, Y,x=0.8-1.1, y=0.5-1.0, 0.9<z<1.1, with a carbon content of 0.5 to 20% byweight, comprising milling of precursors of Li_(x)Mn_(y)M_(1-y)(PO₄)_(z)with electro-conductive carbon black having a specific surface area ofat least 80 m²/g or with graphite having a specific surface area of atleast 9.5 m²/g or with activated carbon having a specific surface areaof at least 200 m²/g and heating to form the lithium manganesephosphate/carbon nanocomposite, wherein a phosphate precursor for theLi_(x)Mn_(y)M_(1-y)(PO₄)_(z) is added in stoichiometric excess withrespect to a metal precursor of the Li_(x)Mn_(y)M_(1-y)(PO₄)_(z).
 4. Theprocess according to claim 1 in which milling is carried out under airor inert gas atmosphere.
 5. The process according to claim 1 carried outin dry conditions or in the presence of a solvent.
 6. The processaccording to claim 1 in which the product of milling is heated forcrystallization to 300-600° C.
 7. The process according to claim 1 inwhich heat treatment is carried out under a vacuum or inert gasatmosphere.
 8. The process according to claim 1 in which heat treatmentis carried out under a reducing gas atmosphere.
 9. The process accordingto claim 1 wherein said metal oxide bonding layer is a manganese oxidebonding layer consisting of either Mn₃O₄ (haussmanite), β-MnO₂(pyrolusite), MnO (manganosite), MnOOH (groutite) or Mn1.85O.6H₂O(birnessite).